Anti-chatter solenoid



May 25, 1965 R. G. FECHO ETAL ANTI-CHATTER SOLENOID Filed July 25, 1963 INVENTORS- Rhine G1'7ec/L0, I .Dcwad CZ kfozz gm j a We 30% United States Patent 3,185,902 ANTI-CHATTER SOLENOID Rhine G. Fecho, Baroda, and David A. Johnson, St. Joseph, Mich., assignors to Whirlpool Corporation, a corporation of Delaware Filed July 25, 1963, Ser. No. 297,566

g 7 Claims. (Cl. 317-184) This invention relates to electromagnetic devices, and in particular to electromagnetic solenoids.

Electromagnetic solenoids are employed for actuation of numerous devices in appliances, such as dishwashers, clothes washing machines, etc. In such devices, it is desir-able to minimize chattering such as may result from the alternating current actuation of the solenoid. Further, it is desirable to prevent sticking of the plunger as from residual magnetism in the magnetic circuit when the electrical energization is discontinued.

It is conventional in such solenoids to provide on the plunger a shading coil which provides a quadrature current whereby a two phase effect is obtained to maintain a positive silent retention of the plunger in its innermost position. The present invention comprehends an improved arrangement in such a solenoid whereby improved silent positive retention of the plunger is obtained while yet free removal of the plunger is permitted upon deenergization of the coil. 7

Thus, a principal feature of the present invention is the provision of a new and improved solenoid structure.

Another feature of the invention is the provision of such a solenoid structure having a new and improved plunger and pole piece construction providing facial engagement therebetween when the solenoid is energized, notwithstanding a skewed relation between the plunger and the axis of the solenoid coil.

A further feature of the invention is the provision of such a solenoid structure including an annular electromagnetic coil defining an axial space, a pole piece at one end of the space and having an inner surface confronting the space, and a plunger axially movable through the space and having an outer surface confronting the pole piece surface, the surfaces being complementarily segmentally spherical and having a radius of curvature substantially equal to one-half the length of the space inwardly from the pole piece surface to the other end of the space, whereby the surfaces may have facial engagement with the plunger skewed substantially to the coil axis.

Still another feature of the invention is the provision of such a solenoid structure including an annular electromagnetic coil including an annular radially inner bobbin defining a cylindrical axial space, a pole piece fixed in one end of the bobbin and having an inner surface confronting the space, and a cylindrical plunger axially movable in the space and having an annular shading coil on its outer end defining an outer surface confronting the pole piece surface, the plunger having a diameter smaller than the diameter of thespace and a length ap proximately equal to the length of the space inwardly from the pole piece surface to the other end of the space, the surfaces being complementarily segmentally spherical and having a radius of curvature approximately equal to one-half the length of the plunger, whereby the surfaces may have facial engagement with the plunger skewed substantially to the coil axis.

Other features and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawing wherein:

FIGURE 1 is a diametric section of a solenoid structure embodying the invention;

FIGURE 2 is a diametric section similar to that of FIGURE 1, but illustrating the arrangement of the 3,185,902 Patented May 25, 1965 ice plunger in skewed relation to the axis of the solenoid coil; and

FIGURE 3 is a transverse section taken substantially along the line 3-3 of FIGURE 1.

In the exemplary embodiment of the invention as disclosed in the drawing, a solenoid structure generally designated 10 is shown to comprise an annular coil 11 provided with a pair of terminals 12 adapted to be connected to a suitable power source (not shown) such as an alternating current power supply. The coil is wound on a spool type bobbin 13in the conventional manner and the assembled coil and bobbin are installed in a permeable metal frame 14 having an upper leg 15 and a lower leg 16 extending transversely to the axis 17 of the coil. A plunger 19 is movable generally axially between seated and unseated positions within the bobbin 13 as a function of the energization of the coil 11 to move forcibly a connector generally designated 20 carried at the upper end of the plunger. The connector 20 may be connected through pin P to the device (not shown) to be actuated by the solenoid, in a conventional manner. FIGURES 1 and 2 illustrate the plunger infully seated position.

As shown in FIGURE 1, solenoid 10 comprises a stopped type solenoid being provided with a pole piece 21 held in frame leg 16 at the lower end of the cylindrical space 22 defined by bobbin 13. Pole piece 21 serves to increase the pull on the plunger 19 when coil 11 is energized and further serves to provide a positive retention of the plunger 19 in the seated, or fully inserted, position shown in FIGURE 1. To preclude chattering of the solenoid when the plunger is in the seated position, a shading coil 23 is mounted on the lower end 24 of the plunger 19 for engagement with the pole piece 21. As shown in FIGURE 1, the shading coil is fixed concentrically on the outer end 24 of the plunger and is provided with a segmentally spherical annular outer surface 25 which has facial engagement with a complementarily segmentally spherical inwardly facing surface 26 on the pole piece 21.

The radius 27 of curvature of surfaces 25 and 26 is preselected to be equal to approximately one-half the length of space 22 between thepole piece 21 and the inner end 28 of the space 22. In the illustrated embodiment, the plunger 19 has a length approximately equal to the length of the space 22 between pole piece 21 and inner end 28, and, thus, the radius 27 is approximately equal to one-half the length of the plunger. Thus, as illustrated in FIGURE 2, the shading coil surface 25 may be in full facial engagement with the pole piece surface 26 in the seated position of the plunger notwithstanding a substantial skewing of the axis 36 of the plunger 19 to the axis 17 of the coil 11. Thus, chattering is effectively eliminated and a positive seated retention of the plunger is obtained.

In the normal assembly process of assembling a solenoid to the device to be actuated, it is practically impossible to assure exact alignment between the line of motion of the device to be actuated and the axis of the solenoid, therefore, as skewing of the plunger 19 normally occurs as a result of a transverse component of force F applied to the connector 20 as from the device to which the connector is connected. Thus, in moving through the space 22, the plunger 19 may be cocked about the center 29 with one point 31 of the plunger sliding along a line 32 on the bobbin 13 parallel to the axis 17 and diametrically opposite to a point 33 on the bobbin at the inner end 28 of the space 22 against which the opposite line portion 34 of the plunger slides during such movement of the plunger. As a result of so locating the center 29 of the radius of curvature of pole piece 27, facial engagement of the shading coil with the pole piece is assured by this self-positioning of the plunger in the seated position of the plunger, as shown in FIGURE 2.

In the illustrated embodiment, as shown in FIGURE 3, each of the plunger 19 and the space 22 are circular in cross-section. The diameter of the plunger is somewhat smaller than the diameter of the space 22, whereby the resultant clearance therebetween permits free movement of the plunger to and from the seated position of FIG- URE 1.

While we have shown and described one embodiment of our invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as defined in the appended claims.

We claim:

1. A solenoid structure comprising: annular electromagnetic coil means defining an axial space; a pole piece at one end of said space and having an inner surface confronting said space; and a plunger axially movable through said space, said plunger having lateral clearance with said coil means and having an outer end defining an outer surface confronting said pole piece surface, said surfaces being complementarily segmentally spherical and having a radius of curvature substantially equal to onehalf the length of said space inwardly from said pole piece surface to the other end of said space, whereby said surfaces may have facial engagement with the plunger disposed in any one of a plurality of positions skewed substantially to the coil axis including a maximum skewed position wherein said outer end of the plunger substantially contacts said coil means.

2. The solenoid structure of claim 1 wherein said plunger includes a shading coil at its outer end, said shading coil defining said outer surface.

3. A solenoid structure comprising: annular electromagnetic coil means defining a cylindrical axial space; a pole piece at one end of said coil and having an inner surface confronting said space; and a cylindrical plunger axially movable in said space, said plunger having lateral clearance with said coil means and having an outer end defining an outer surface confronting said pole piece surface, said plunger having a diameter smaller than the diameter of said space, said surfaces being complementarily segmentally spherical and having a radius of curvature substantially equal to one-half the length of said space inwardly from said pole piece surface to the other end of said space, whereby said surface may have facial engagement with the plunger disposed in any one of a i plurality of positions skewed substantially to the coil axis including a maximum skewed position wherein said outer end of the plunger substantially contacts said coil means.

4. The solenoid structure of claim 3 wherein said pole piece is disposed within said space.

5. The solenoid structure of claim 3 wherein said plunger has a length approximately equal to the length of said space inwardly from said pole piece surface to the other end of said space, and said radius of curvature is equal to approximately one-half the length of said plunger.

6. The solenoid structure of claim 3 wherein said coil is provided with a radially inner, annular bobbin defining said space, whereby said plunger may have sliding engagement with said bobbin during axial movement of the plunger in said space.

7. A solenoid structure comprising: annular electro: magnetic coil means including an annular radially inner bobbin defining a cylindrical axial space; a pole piece fixed in one end of said bobbin and having an inner surface confronting said space; and a cylindrical plunger axially movable in said space, said plunger having lateral clearance with said bobbin and having an outer end and an annular shading coil on said outer end defining an outer surface confronting said pole piece surface, said plunger having a diameter smaller than the diameter of said space and a length approximately equal to the length of said space inwardly from said pole piece surface to the other end of said space, said surfaces being complementarily segmentally spherical and having a radius of curvature approximately equal to one-half the length of said plunger, whereby said surfaces may have facial engagement with the plunger disposed in any one of a plurality of positions skewed substantially to the coil axis including a maximum skewed position wherein said outer end of the plunger substantially contacts said bobbin.

References Cited by the Examiner UNITED STATES PATENTS 852,773 5/07 Copeman. 2,734,153 2/56 Soreng et al 317-186 X FOREIGN PATENTS 690,635 5/40 Germany.

JOHN F. BURNS, Primary Examiner.

LARAMIE E. ASKIN, Examiner. 

1. A SOLENOID STRUCTURE COMPRISING: ANNULAR ELECTROMAGNETIC COIL MEANS DEFINING AN AXIAL SPACE; A POLE PIECE AT ONE END OF SAID SPACE AND HAVING AN INNER SURFACE CONFRONTING SAID SPACE; AND A PLUNGER AXIALLY MOVABLE THROUGH SAID SPACE, SAID PLUNGER HAVING LATERAL CLEARANCE WITH SAID COIL MEANS AND HAVING AN OUTER END DEFINING AN OUTER SURFACE CONFRONTING SAID POLE PIECE SURFACE, SAID SURFACES BEING COMPLEMENTARILY SEGMENTALLY SPHERICAL AND HAVING A RADIU OF CURVATURE SUBSTANTIALLY EQUAL TO ONEHALF THE LENGTH OF SAID SPACE INWARDLY FROM SAID POLE PIECE SURFACE TO THE OTHER END OF SAID SPACE, WHEREBY SAID SURFACES MAY HAVE FACIAL ENGAGEMENT WITH THE PLUNGER DISPOSED IN ANY ONE OF A PLURALITY OF POSITIONS SKEWED SUBSTANTIALLY TO THE COIL AXIS INCLUDING A MAXIMUM SKEWED POSTION WHEREIN SAID OUTER END OF THE PLUNGER SUBSTANTIALLY CONTACTS SAID COIL MEANS. 